1. Field of the Invention
The present invention relates to a method and apparatus for reduced radius turning for large gantry type cranes which run on rails or tracks, and more particularly, to a means for lifting a portion of the sets of wheels which support the crane whereby the radius for the turns in the tracks can be substantially shortened.
2. Description of the Prior Art
Prior to the development of the present invention, it was necessary in order for a large gantry crane to traverse a turn or curve on its support rails that the radius of the curve be made large enough so that the flanged wheels of the bogies on which the crane rides do not bind with the rails. If the radius of the curve is small, the flanges on the wheels which keep the wheels on the rails cannot track during the traverse of the curve without binding with the vertical sides of the rails. This arrangement therefore requires relatively large radius turns in the tracks, and for large cranes this is unsatisfactory due to the high-cost of space in a cargo handling area and the resulting loss of utilization thereof. This is of particular importance in a port area alongside docks which are used for loading and unloading cargo container ships and adjacent to high density storage areas where these cranes operate, as well as for allowing cranes to turn corners to run on adjacent perpendicular docks.
Until the present invention, there has been no known way of having large cranes negotiate shorter-radius turns than the standard bogies were capable of handling while providing the same degree of stability required for loading and unloading operations as with standard bogie arrangements.